The airways of patients with chronic bronchitis are persistently colonized by various bacterial species in contrast to the airways of normal subjects which are sterile. If is postulated that this persistent colonization is related to the continuing bronchial inflammation associated with chronic bronchitis and to the recurrent episodes of purulent infection. The hypothesis underlying the proposed research is that bacterial colonization of the airways in chronic bronchitis is due to adherence of the colonizing species to bronchial epithelial cells. Similar adherence has been shown to be a powerful determinant of bacterial colonization and infection of other mucosal surfaces. In the planned studies, bronchial epithelial cells will be obtained from volunteers by bronchial brushing via a fiberoptic bronchoscope. Study subjects will include nonsmoking normal people, smokers without disease, smokers with chronic bronchitis, and smokers with bronchitis and chronic airflow obstruction. Bronchial epithelial cells will be studied to determine: (1) whether bacteria are adherent to their surface in vivo, and (2) the attachment to selected organisms to their surface in vitro. Adherence findings will be correlated with bacteriologic evaluation of expectorated secretions. An additional group of subjects with recurrent episodes of acute bronchitis will be studied before, during, and after such an episode to determine the effects of acute episodes on bronchial cell adherence properties. If our hypothesis is correct, these studies will lead to investigation of the mechanisms of bacterial adherence, its alteration in chronic bronchitis, and possibly to new approaches to the treatment of this disease.